Analyzing the Effect of Yarn and Knitting Parameters on Ultraviolet Radiation Protection by Taguchi Experimental Design

Transcription

1 Analyzing the Effect of Yarn and Knitting Parameters on Ultraviolet Radiation Protection by Taguchi Experimental Design Prithwiraj Mal Department of Textile Design, National Institute of Fashion Technology, Hyderabad, Telangana Abhijit Majumdar, PhD Department of Textile Technology, Indian Institute of Technology, New Delhi, Anindya Ghosh, PhD Department of Textile Technology, Government College of Engineering and Textile Technology Berhampore, West Bengal, Debamalya Banerjee, PhD Department of Production Engineering, Jadavpur University, Kolkata, West Bengal, Correspondence to: Prithwiraj Mal ABSTRACT The ultraviolet protection factors (UPF) of single jersey and 1 1 rib knitted fabrics have been investigated using Taguchi experimental design. The effects of loop length, knitting speed or carriage speed, yarn input tension and yarn fineness have been studied in the presence of two unavoidable and uncontrolled noise. The results show that the yarn count and loop length have significant impact on the UPF for both single jersey and 1 1 knitted fabrics. A ranking of the four controlled and the percentage contribution of each of these have also been determined. The optimum that correspond to the highest S/N ratio of UPF have also been evaluated. INTRODUCTION Sunlight, which is the major source of Vitamin D for the human body, constitutes rays of different wavelength (both in the visible and invisible range). Exposure of the human body to sunlight helps in the synthesis of vitamin D, which is essential for the proper metabolism of calcium [1-3]. Researchers have studied the physiological and biological responses of human body to sunrays or solar radiation. For example, lights have been used for the treatment of neonatal jaundice, a disease common to infants or for the treatment of chronic skin disease psoriasis [4-5]. However, solar rays are filtered by the atmosphere (by the layer of ozone), which removes the ultraviolet (UV) radiation having wavelengths less than 290 nm. Thus, the solar radiation which reaches the earth surface consists of ultraviolet rays ( nm), visible rays ( nm), and infrared rays (more than 770 nm). The UV rays have significant impact on human health, affecting the skin, immune system, eye etc. [6-8]. The UV rays affect the top layer of the skin, leading to premature aging, roughing, wrinkles and basal cell cancer. Textile fabrics are used to protect our skin from the dangerous UV rays. Therefore, designing an outerwear textile with optimum comfort and desired UV protection is a big challenge. The UV protection capability of a fabric is expressed by UPF (ultraviolet protection factor). A higher value of UPF indicates more protection against the UV radiation. The UPF of a fabric depends on fiber type, yarn properties, tightness factor or cover factor, areal density, color, finishing, etc. [9-16]. Knitted fabrics are commonly used in most of the outdoor sports garments. The porous structure of the knitted fabric provides good warmth and permeability. However, the relatively open structure of knitted fabrics may not provide adequate protection against the UV radiation. The openness of the knitted fabric can be tuned by varying the yarn count and loop length. In this study Taguchi design methods are used to study the effect Journal of Engineered Fibers and Fabrics 26

2 of loop length, knitting speed or carriage speed, yarn input tension and yarn fineness on UPF of single jersey and 1 1 rib knitted fabrics considering the unavoidable noise - position in the knitting machine and yarns from different cones. Also, optimum levels of different controlled for maximum UPF have been determined. MATERIALS AND METHOD Materials Knitted fabrics are formed by a process called interlooping. The vertical loops constitute wales whereas the horizontal rows of loops form the courses. The loops are intermeshed in various ways to produce various knitted structure. The length of the yarn required to form one loop is known as loop length. The two most popular knitted structures are single jersey and 1 1 rib. Figure 1 and Figure 2 depict the single jersey and 1 1 rib knitted fabrics, respectively. FIGURE 1.. Yarns spun from 0% cotton fibers were used to produce 36 single jersey and 36 rib (1 1) knitted fabrics on a computerized flat knitting machine. Four controlled, namely loop length, carriage speed, yarn input tension and yarn counts, were systematically varied for the sample preparation. For each controlled parameter, three levels were taken. Constant yarn feed mechanism was used during knitting to maintain the loop length at desired level. Two different noise were introduced in this study i.e. samples were made from two different cones and at two different positions in the knitting machine (right side and left side). and 1 1 rib knitted fabric samples were prepared according to the L9 orthogonal array as shown in Table I. The actual values of the controlled and noise corresponding to their coded levels are shown in Table II and Table III, respectively. Testing All the single jersey and rib knitted fabric were completely relaxed by washing in a Washcator washing machine as per the EN ISO 63. The samples were then conditioned at standard temperature of + 2 o C and % relative humidity for 48 hours. Subsequently, the samples were evaluated for UV protection. For each of 72 fabric types, samples were evaluated for UPF and the mean values were taken. The ultraviolet protection factor (UPF) is a rating which indicates how effectively the fabric blocks UV rays. The UPF of the samples were determined by the in-vitro method, according to the AATCC 183:04 standard. The UV transmittance analyzer (Labsphere 00F) was used to measure the UPF of samples. The UV transmittance was measured in steps of 1 nm wavelength by passing ultraviolet rays through the fabric. The UPF was calculated using the following equation. (1) where E(λ) is the relative erythemal spectral effectiveness, S(λ) is the solar spectral irradiance [Wm -2 nm -1 ], Δλ = measured wavelength interval [nm] and T(λ) = average spectral transmittance of the sample. FIGURE rib. Journal of Engineered Fibers and Fabrics 27

3 TABLE I. L9 (3 4 ) orthogonal array. Experimental Controlled Uncontrolled run Cone Knitting X 1 X 2 X 3 X 4 no. position TABLE II. Controlled and their levels. Controlled Loop length (mm), X 1 Carriage speed (m/s), X 2 Yarn input tension (cn), X 3 Yarn count (Ne), X 4 Coded level 1 1 rib TABLE III. Uncontrolled and their levels. Coded Level Uncontrolled 1 1 rib Cone no Left Right Left Right Knitting position side side side side Analysis of the Response The Taguchi method is a statistical approach developed by Genichi Taguchi [17]. It has become an important tool in engineering to improve the quality of manufactured products by minimizing the effect of causes of variation. A special set of arrays known as orthogonal arrays and signal to noise ratio (S/N) are used in Taguchi method. In orthogonal arrays, a special set of arrays of and levels combination are used to conduct minimum number of experiments determine all that influence the response. A typical L9 orthogonal array is shown in Table I. It consists of four with three levels each. The value 9 indicates nine prototypes that need to be tested. X 1, X 2, X 3 and X 4 in the table are the controlled. The experimental outputs are then transformed into a Signal to Noise ratio (S/N ratio) that represents the ratio of sensitivity to variability. A higher S/N ratio indicates better quality. The S/N ratio needs to be maximized, thus minimizing the effect of uncontrolled random noise factors that may influence the process performance at significant level. It can be calculated using the following equations, yielding three possible responses: larger-the-better, smaller-the-better or nominal-the-best [17-19]. a) Nominal the best b) Larger the better c) Smaller the better (2) (3) (4) where, is mean of observed data, S 2 y is the variance of y, n is the number of experiments in the orthogonal array and y i is the i th value measured. In this experiment, S/N ratios of the UPF have been calculated based on the Eq. (3) for larger-the-better. Optimum process can be determined henceforth. For each significant factor, the level corresponding to the highest S/N ratio is the optimum level. The response of S/N for UPF gives the rank of the controlled. An ANOVA analysis of the S/N ratio is also done to understand the percentage contribution of each controlled parameter. RESULTS AND DISCUSSION The experimental results of average UPF and their calculated S/N ratios (larger-the-better) for both single jersey and 1 1 rib knitted fabrics are shown in Table IV. The response of S/N ratios of UPF are shown in Table V, whereas, the ANOVA analysis conducted on UPF are presented in Table VI for both single and 1 1 rib fabrics. Figure 3 depicts the effect of the controllable on S/N ratio of UPF for both for single jersey and 1 1 rib knitted fabrics. Table IV shows that the highest S/N ratios of UPF are and for single jersey and 1 1 rib fabrics, respectively. The optimum corresponding to the maximum S/N ratio of UPF for single jersey fabric are 6.6 mm, 0.25 m/s, 6 cn and 5 Ne, respectively for loop length, carriage speed, yarn tension and yarn count. In case of 1 1 rib fabric, the levels configuration for highest S/N ratio for UPF are Journal of Engineered Fibers and Fabrics 28

4 5.09 mm, 0.25 m/s, 6 cn and 5 Ne for loop length, carriage speed, yarn tension and yarn count, respectively. The response for S/N ratios which are presented in Table V clearly shows that the yarn count has the highest impact on UPF followed by loop length, yarn input tension and carriage speed for single jersey fabric. In case of 1 1 rib fabric, yarn count has highest impact on UPF followed by loop length, carriage speed and yarn input tension. Table VI computes the percentage contribution of different on UPF. It is evident from the Table VI that the yarn count is the most dominant factor influencing the UPF with a contribution of 97% and 94.4% for single jersey and 1 1 rib fabrics, respectively. The next highest factor affecting UPF is the loop length which only contributes 2.1% and 5.1% for single jersey and 1 1 rib fabrics, respectively. In this study, the fabric tightness factor and areal density change considerably with the change in yarn count as compared to that of loop length. Thus the effect of yarn count on UPF is much more pronounced than that of loop length. Tightness factor of knitted fabric indicates the area covered by the yarn within a repeat area of a fabric. The tightness factor of a single jersey knitted fabric can be expressed as: Tightness factor = (5) where K s is a constant, l is loop length and Ne is the yarn count. Higher tightness factor of a fabric implies more cover which does not allow the UV rays easily to pass through it. Besides, higher areal density of a fabric corresponds to higher UV ray absorption by the fabric. It is also evident from the Table II that the percentage change in yarn count from lower level to the upper level is 0% (from 5 Ne to Ne), which causes a decrease in tightness factor by 29.3% for single jersey fabrics [Eq. (5)]. Again, the percentage change from lower level to the upper level of loop length is only 11.8%, which corresponds to change of tightness factor by only.8% [Eq. (5)]. For, 1 1 rib fabrics, similar effects are observed. This may be explained in the similar lines as discussed for single jersey fabrics. Yarn input tension and carriage speed have little effect on the UPF because these two have no significant influence on the fabric tightness factor and areal density, as no change in loop length occurs due to 'robbing off' that arises due to tension variation in the loop formation region of knitting machine. The loop length is maintained to its desired level throughout knitting using constant yarn feed mechanism. It is also evident from the Figure 3 that for both single jersey and 1 1 rib knitted fabrics, the UPF decreases with the increase in loop length and yarn count. Higher loop length and finer yarn count reduce the tightness factor of fabric that leads to lower UPF and vice - versa. The change of carriage speed and yarn input tension have negligible influence on UPF as they have no major influence on the tightness factor and areal density while knitting using constant feed mechanism. TABLE IV. Average values of UPF and S/N ratios. Parameters and their levels 1 1 rib Exp. No. X 1 X 2 X 3 X 4 Average UPF S/N ratio Average UPF S/N ratio Journal of Engineered Fibers and Fabrics 29

5 TABLE V. Response for S/N ratios of UPF. 1 1 rib Factors Average S/N Average S/N Range Rank Range Rank Level -1 Level 0 Level +1 Level -1 Level 0 Level +1 X X X X Factors Sum of squares TABLE VI. ANOVA summary conducted on S/N ratios of UPF. Degree of freedom Mean square Percentage contributio n Sum of squares Degree of freedom 1 1 rib Mean square Percentage contributio n X X X X Total Loop length (mm) Speed (m/s) 6 8 Input tension (cn) Yarn count (Ne) FIGURE 3. S/N ratio plot of UPF with change in various for single jersey and 1 1 rib fabric. CONCLUSION In this work, the influence of yarn and knitting affecting the UPF has been studied using Taguchi experimental design. Based on the S/N ratio and ANOVA analysis, it was found that the yarn count and loop length are the most significant affecting the UPF. This is due to the fact that higher tightness factor prevents UV penetration and high areal density for a given tightness facilitates more absorption of UV rays. The other controllable such as input yarn tension and carriage speed have negligible effect on UPF due to constant yarn feed during knitting, which nullifies the change in loop length. The relative contribution of yarn count and loop length to the UPF of fabrics was almost same for single jersey and 1 1 rib knitted fabrics. Journal of Engineered Fibers and Fabrics

6 REFERENCES [1] Holick, M. F., Vitamin D: A Millennium Perspective, Journal of Cellular Biochemistry, 88, (03) [2] Holick, M. F., Resurrection of Vitamin D Deficiency and Rickets, Journal of Clinical Investigation, 116, (06) [3] Pettifor, J. M., Nutritional Rickets: Deficiency of Vitamin D, Calcium, or Both, The American Journal of Clinical Nutrition, 80, (04) 1725S 1729S. [4] Bonjar, A. H. S., UV Phototherapy Has Positive Effect in Viral Treatments, International Journal of Applied Science and Technology, 2, (12) 2 5 [5] Masood, Q., Majid, I., Photochemotheraphy and Its Variants: Safe and Useful Modes of Therapy, International Journal of Current Medical Science and Practice, 11, (04) [6] Mackie, R. M., Effects of Ultraviolet Radiation on Human Health, Radiation Protection Dosimetry, 91, (00) [7] Gallagher, R. P., Lee, T. K., Adverse Effects of Ultraviolet Radiation: A Brief Review, Progress in Biophysics and Molecular Biology, 92, (06) [8] Halliday, G. M., Norval, M., Byrne, S. N., Huang, X. X., Wolf, P., The Effects of Sunlight on the Skin, Drug Discovery Today, 5, 08, e1 e9. [9] Dubrovski, P. D., Woven Fabrics and Ultraviolet Protection, In: Duvrovski, P. D., ed. Woven Fabric Engineering, Sciyp, India, () [] Das, B. R., UV Radiation Protective Clothing, Open Textile Journal, 3, () [11] Majumdar, A., Kothari, V. K., Mondal, A. K.., Hatua, P., Effect of Weave, Structural Parameters and Ultraviolet Absorbers on In Vitro Protection Factor of Bleached Cotton Woven Fabrics, Photodermatology, Photoimmunology & Photomedicine, 28, (08) [12] Algaba, I. M., Pepio, M., Riva, A., Correlation Between the Ultraviolet Protection Factor and the Weight and Thickness of Undyed Cellulosic Woven Fabrics, Fibres & Textiles in Eastern Europe,16, (08) [13] Algaba, I., Riva, A., Influence of Fibre Type and Fabric Porosity on the UPF of Summer Fabrics, AATCC Review, (04) [14] Morihiro, Y., Eri, F., Chie, T., Effects of Fiber Materials and Fabric Thickness on UV Shielding Properties of Fabrics, Journal of Textile Engineering, 55 (09), 3 9. [15] Hang-kei, S. C., Chi-wai K., Jimmy, K. L., Sunpui, N., Hong, H., Chun-wah, M. Y., Study on the Relationship Between UV Protection and Knitted Fabric Structure, Journal of Textile Engineering, 59, (13) [16] Eddie, L. Y., Chi-wai, K., Jimmy, K. L., Sunpui, N., Hong, H., Chun-wah, M. Y., The Relationship Between Ultraviolet Protection Factor and Fibre Content, Journal of Textile Engineering, 59, (13) [17] Taguchi, G., Chowdhury, S., and, Wu, Y., Taguchi s Quality Engineering Handbook, John Wiley & Sons, (05) [18] Ross, P. J., Taguchi Techniques for Quality Engineering, McGraw-Hill International Editions, (1996) [19] Roy, R. K., Design of Experiments Using the Taguchi Approach, Wiley-Interscience Publication, (01) AUTHORS ADDRESSES Prithwiraj Mal National Institute of Fashion Technology Department of Textile Design NIFT Campus Opposite Hi-Tech City, Madhapur Hyderabad, Telangana 0081 Abhijit Majumdar, PhD Department of Textile Technology Indian Institute of Technology, Delhi Hauz Khas, New Delhi New Delhi 1016 Anindya Ghosh, PhD Department of Textile Technology Government College of Engineering and Textile Technology, Berhampore West Bengal 7421 Debamalya Banerjee Department of Production Engineering, Jadavpur University, Kolkata, West Bengal Journal of Engineered Fibers and Fabrics 31